Dispersal Mechanisms Research Articles

Dynamics of dispersal: Modeling the impact of dandelion proliferation on environmental and economic equilibria

Dandelion, with its unique wind dispersal mechanism, can easily spread its seeds across vast land areas, encroaching on territories of other creatures. To address this issue, two models are considered: The first model considers wind patterns, temperature, and moisture in dandelion growth, using differential equations to analyze population changes over time. Sensitivity analysis reveals the models responsiveness to these factors. The second model combines ecological and economic factors to assess the impact of invasive species, employing fuzzy mathematics to determine the severity of impact. The study identifies Canada Goldenrod as particularly destructive. These models offer insights for future invasive species management policies, showcasing innovations in incorporating partial differential functions and fuzzy mathematics for more accurate estimations.

Numerical simulation of agricultural unmanned helicopter corn canopy spraying

Plant protection by unmanned aerial vehicle (UAV) is a highly complicated process, especially considering the vast and diversified crop canopy. Furthermore, the droplet dispersal mechanism above and inside the crop canopy remains unclear. Owing to this, the authors used the lattice Boltzmann method (LBM) to simulate the application of plant protection UAV. The LBM is suitable not only to simulate the rotor tip vortex of UAV but also to model the crop canopy with detailed geometry. It is found that the streamwise and spanwise speed of the downwash flow achieve an extreme value both on top of the corn canopy and near the ground. When the droplet diameter decreased from 400 to 50 μm, its deposit region width doubled and its floating time increased from 3 s to more than 12 s. Small droplets are more likely to be lifted by the secondary flow near the ground and drift for a longer distance, while larger droplets are deposited directly. The increase in application height weakened the secondary spanwise flow near the ground and caused less droplet re-lifting and spanwise movement. The best point to initiate and terminate spraying is 2.5 m after passing the target corn canopy region. The droplet penetration rate in the canopy decreased with an increase in droplet size. This study used the LBM to model the unmanned helicopter application on a full corn canopy. Droplet deposition and distribution correspond to droplet size and canopy structure. The simulation results establish a foundation to optimize agricultural aerial spraying in an efficient and methodical manner.

Dispersion Behavior of a Droplet Impacting a Single Fiber.

The high-gravity reactor, known for its excellent mass transfer capability, plays a crucial role in the carbon capture process. The wire mesh packing serves as the core structure for enhancing mass transfer performance. Understanding the underlying dispersion mechanism requires a thorough exploration of the dynamics of droplet impact on a single fiber. This work aimed to numerically study the process of a droplet impacting a single fiber by applying the volume of fluid method. The effects of initial velocity (u0), initial diameter (D0), impact eccentric distance (e), and impact angle (θ) on the deformation evolution and dispersion characteristics of a droplet impacting a single fiber were systematically studied. Central or vertical impacts can be categorized into four main stages: splitting, merging, stretching, and breaking. Meanwhile, asynchronous breaking, sliding splitting, and oblique stages were observed during eccentric and nonvertical impacts. Subsequently, dimensionless time (t*) and the rate of increase of the gas-liquid interfacial area (η) were introduced to quantitatively analyze the dispersion characteristics postimpact. Increasing the initial velocity, reducing the droplet diameter, minimizing the impact eccentric distance, and maximizing the impact angle all contribute to enhanced dispersion performance. A correlation for the maximum increase rate of the gas-liquid interfacial area of the droplet was proposed, with errors less than ±15%. Finally, the deformation mechanism of droplet impact on a fiber was summarized by analyzing the influences of differential pressure inside and outside the liquid film, as well as gas vortices.

Floral Biology of Chinar (Platanus orientalis L.) under Temperate Conditions in the Kashmir Himalayas

Chinar, Platanus orientalis is a huge, widely distributed, and long-lived deciduous tree native to the eastern Mediterranean. It is the only species of the Platanaceae family found in India and grows throughout the valley. Since ancient times, this particular species has garnered fascination and reverence, leading to its continuous examination and admiration. However, the information related to its floral biology is meagre. The floral biology of P. orientalis is crucial to understanding its reproductive mechanisms and ecological interactions. The present study, therefore, aimed at investigating the floral characteristics of P. orientalis. For this study, seven young sexually mature trees were selected to study the floral characteristics. It was revealed that, in general, male flowers often emerge earlier than female blosssoms. The position of the male flower is always proximal and that of the female flower is distal when present on terminal branches. The average male female ratio recorded was 7:1 and the ratio between pollen and ovules on average was 9550 to 1. The pollen-ovule ratio is a fundamental reproductive parameter that provides insights into the reproductive strategies and ecological adaptations of plant species. The floral biology of P. orientalis demonstrates its adaptation to wind pollination and efficient seed dispersal mechanisms. This knowledge enhances comprehension and aids in gaining a deeper understanding of the reproductive strategies of P. orientalis and its ecological significance within its native range. Research in this field can help in developing effective conservation strategies and utilizing this species for research purposes.

On the analysis of optical pulses to the fractional extended nonlinear system with mechanism of third-order dispersion arising in fiber optics

On the analysis of optical pulses to the fractional extended nonlinear system with mechanism of third-order dispersion arising in fiber optics

Non-monotonic effect of compaction on longitudinal dispersion coefficient of porous media

Utilizing the discrete element method and the pore network model, we numerically investigate the impact of compaction on the longitudinal dispersion coefficient of porous media. Notably, the dispersion coefficient exhibits a non-monotonic dependence on the degree of compaction, which is distinguished by the presence of three distinct regimes in the variation of dispersion coefficient. The non-monotonic variation of dispersion coefficient is attributed to the disparate effect of compaction on dispersion mechanisms. Specifically, the porous medium tightens with an increasing pressure load, reducing the effect of molecular diffusion that primarily governs at small Péclet numbers. On the other hand, heightened pressure loads enhance the heterogeneity of pore structures, resulting in increased disorder and a higher proportion of stagnant zones within porous media flow. These enhancements further strengthen mechanical dispersion and hold-up dispersion, respectively, both acting at higher Péclet numbers. It is crucial to highlight that hold-up dispersion is induced by the low-velocity regions in porous media flow, which differ fundamentally from zero-velocity regions (such as dead-ends or the interior of permeable grains) as described by the classical theory of dispersion. The competition between weakened molecular diffusion and enhanced hold-up dispersion and mechanical dispersion, together with the shift in the dominance of dispersion mechanisms across various Péclet numbers, results in multiple regimes in the variation of dispersion coefficients. Our study provides unique insights into structural design and modulation of the dispersion coefficient of porous materials.

Spatial prioritization for widespread invasive species control: Trade-offs between current impact and future spread.

Spatially explicit prioritization of invasive species control is a complex issue, requiring consideration of trade-offs between immediate and future benefits. This study aimed to prioritize management efforts to account for current and future threats from widespread invasions and examine the strength of the trade-off between these different management goals. As a case study, we identified spatially explicit management priorities for the widespread invasion of introduced willow into riparian and wetland habitats across a 102,145-km2 region in eastern Australia. In addition to targeting places where willow threatens biodiversity now, a second set of management goals was to limit reinfestation and further spread that could occur via two different mechanisms (downstream and by wind). A model of likely willow distribution across the region was combined with spatial data for biodiversity (native vegetation, threatened species and communities), ecological conditions, management costs, and two potential dispersal layers. We used systematic conservation planning software (Zonation) to prioritize where willow management should be focussed across more than 100,000 catchments for a range of different scenarios that reflected different weights between management goals. For willow invasion, we found that we could prioritize willow management to reduce the future threat of dispersal downstream with little reduction in the protection of biodiversity. However, accounting for future threats from wind dispersal resulted in a stronger trade-off with protection of threatened biodiversity. The strongest trade-off was observed when both dispersal mechanisms were considered together. This study shows that considering current and future goals together offers the potential to substantially improve conservation outcomes for invasive species management. Our approach also informs land managers about the relative trade-offs among different management goals under different control scenarios, helping to make management decisions more transparent. This approach can be used for other widespread invasive species to help improve invasive species management decisions.

Influence of Temperatures on Physicochemical Properties and Structural Features of Tamarind Seed Polysaccharide.

Due to the high content of impurities such as proteins in tamarind seed polysaccharide (TSP), they must be separated and purified before it can be used. TSP can disperse in cold water, but a solution can only be obtained by heating the mixture. Therefore, it is important to understand the dispersion and dissolution process of TSP at different temperatures to expand the application of TSP. In this study, pasting behavior and rheological properties as a function of temperature were characterized in comparison with potato starch (PS), and their relationship with TSP molecular features and microstructure was revealed. Pasting behavior showed that TSP had higher peak viscosity and stronger thermal stability than PS. Rheological properties exhibited that G' and G'' of TSP gradually increased with the increase in temperature, without exhibiting typical starch gelatinization behavior. The crystalline or amorphous structure of TSP and starch was disrupted under different temperature treatment conditions. The SEM results show that TSP particles directly transformed into fragments with the temperature increase, while PS granules first expanded and then broken down into fragments. Therefore, TSP and PS underwent different dispersion mechanisms during the dissolution process: As the temperature gradually increased, TSP possibly underwent a straightforward dispersion and was then dissolved in aqueous solution, while PS granules initially expanded, followed by disintegration and dispersion.

Dynamic evaporation characteristics of liquefied natural gas droplets

To delve into the intricate evaporation and dispersion mechanisms of dense droplets formed in the vicinity of liquefied natural gas (LNG) accidental releases, it is imperative to first examine the evaporation dynamics of individual moving LNG droplets. This paper presents a visual experimental setup designed to scrutinize the temporal evolution of diameter and displacement of single free-falling LNG droplets. Additionally, eight typical drag force models used for droplet motion state calculations were assessed. The optimal drag force models were selected to accurately predict the displacement of LNG droplets in the wide range of 100 < Re < 10 000. Moreover, eight typical gas phase models applied to predict heat and mass transfer were evaluated, revealing that none accurately capture the dynamic evaporation of free-falling LNG droplets. Subsequently, a new gas phase model suitable for predicting LNG droplet evaporation behavior is proposed. Furthermore, the periodic oscillation behavior of LNG droplet shape during the falling process is uncovered. The oscillation amplitude and dominant frequency of droplets are quantitatively investigated using the aspect ratio of droplets. Finally, an in-house program is developed to comprehensively analyze the evaporation characteristics of LNG droplets under different initial droplet diameters, velocities, and ambient temperatures. Based on gray relational analysis, the relative importance of three impacting factors on the evaporation coefficient is ranked.

Climate change may shift metapopulations towards unstable source-sink dynamics in a fire-killed, serotinous shrub.

Climate change, with warming and drying weather conditions, is reducing the growth, seed production, and survival of fire-adapted plants in fire-prone regions such as Mediterranean-type ecosystems. These effects of climate change on local plant demographics have recently been shown to reduce the persistence time of local populations of the fire-killed shrub Banksia hookeriana dramatically. In principle, extinctions of local populations may be partly compensated by recolonization events through long-distance dispersal mechanisms of seeds, such as post-fire wind and bird-mediated dispersal, facilitating persistence in spatially structured metapopulations. However, to what degree and under which assumptions metapopulation dynamics might compensate for the drastically increased local extinction risk remains to be explored. Given the long timespans involved and the complexity of interwoven local and regional processes, mechanistic, process-based models are one of the most suitable approaches to systematically explore the potential role of metapopulation dynamics and its underlying ecological assumptions for fire-prone ecosystems. Here we extend a recent mechanistic, process-based, spatially implicit population model for the well-studied fire-killed and serotinous shrub species B. hookeriana to a spatially explicit metapopulation model. We systematically tested the effects of different ecological processes and assumptions on metapopulation dynamics under past (1988-2002) and current (2003-2017) climatic conditions, including (i) effects of different spatio-temporal fires, (ii) effects of (likely) reduced intraspecific plant competition under current conditions and (iii) effects of variation in plant performance among and within patches. In general, metapopulation dynamics had the potential to increase the overall regional persistence of B. hookeriana. However, increased population persistence only occurred under specific optimistic assumptions. In both climate scenarios, the highest persistence occurred with larger fires and intermediate to long inter-fire intervals. The assumption of lower intraspecific plant competition caused by lower densities under current conditions alone was not sufficient to increase persistence significantly. To achieve long-term persistence (defined as >400 years) it was necessary to additionally consider empirically observed variation in plant performance among and within patches, that is, improved habitat quality in some large habitat patches (≥7) that could function as source patches and a higher survival rate and seed production for a subset of plants, specifically the top 25% of flower producers based on current climate conditions monitoring data. Our model results demonstrate that the impacts of ongoing climate change on plant demographics are so severe that even under optimistic assumptions, the existing metapopulation dynamics shift to an unstable source-sink dynamic state. Based on our findings, we recommend increased research efforts to understand the consequences of intraspecific trait variation on plant demographics, emphasizing the variation of individual traits both among and within populations. From a conservation perspective, we encourage fire and land managers to revise their prescribed fire plans, which are typically short interval, small fires, as they conflict with the ecologically appropriate spatio-temporal fire regime for B. hookeriana, and likely as well for many other fire-killed species.

Interaction mechanisms between fibers and bubbles during foam forming

It is critical to understand the interaction mechanism of fiber-bubble before the foam-forming technique is used to disperse the long fiber and tailor the material microporous structure. Herein, the adhesion behavior of ionic and nonionic surfactants with different concentrations on five fibers was investigated, and the effect of electrostatic force and adhesion driving force on the interaction between fibers and bubbles was analyzed. In addition, the fiber dispersion mechanisms and the response mechanism of the fiber orientation and tensile strength of foam-formed paper on the interaction strength between fiber and bubble were clarified. The results show that the adhesion ability between hydrophobic fibers with weak surface polarity and cationic and amphoteric surfactants is more obvious. Though electrostatic repulsion weakens the interaction strength of fibers with anionic surfactants, the adhesion ability can exist when the adhesion driving force is larger than 6.6 mN/m. Furthermore, the bridge effect between ethoxylated surfactant headgroups with the acylamino on the aramid fiber surface also propels the adhesion behavior of bubble-fiber. The fiber dispersion mechanisms were proposed based on the adhesion effect of the fiber-bubble, electrostatic elimination, and high-viscosity (≥95 mPa∙s) properties of the “foam-fiber” slurry. Eventually, under the gradually decreased interaction strength between fibers and bubbles, the fiber orientation in the Z direction of foam-formed NBSKP fiber paper turned from −20°-20° to −60°-40°, and the tensile strength decreased from 693 KPa to 537 KPa. This work has implications for improving the long fiber dispersion and regulating the structure of foam-formed fiber composites.

Dynamics of radionuclide electromigration in intact granite: An kinetic adsorption-advection-dispersion model and its application

Granite, as the natural barrier for the disposal of high-level radioactive waste, plays an important role in ensuring environmental and public safety. The safety assessment of the repository depends on the reliable migration parameters of radionuclides in granite. In this study, we developed a kinetic adsorption-advection-dispersion model based on first-order adsorption kinetics. It introduces a first-order adsorption rate coefficient to describe the kinetics of adsorption process and accounts for other crucial mechanisms affecting the migration of radionuclide ions, namely, the electromigration, electroosmosis, and dispersion. This model is then applied to interpret the experimental results of electromigration of tracer ions in intact granite. The results show that for the weakly adsorbed radionuclides studied, iodide and selenite, the effective diffusion coefficients and formation factors calculated by this model are in constant with those derived from the classical advection-dispersion model based on linear adsorption equilibrium. By contrast, for the moderately or strongly adsorbed tracer ions studied, including cobalt, cesium, and strontium, the migration parameters calculated by this model exhibit significantly less uncertainty than those obtained from the advection-dispersion model simulations. The advection-dispersion model based on the first order adsorption kinetics introduces the first order adsorption rate coefficient, and considers the influence of electromigration, electroosmosis and dispersion mechanism, which helps to explain the migration mechanism of nuclide ions in intact granite more accurately.

Nanotechnology in the Fabrication of Advanced Paints and Coatings: Dispersion and Stabilization Mechanisms for Enhanced Performance

AbstractThis review comprehensively analyzes the challenge of dispersing and stabilizing of various common nanomaterials (NMs), including TiO₂, SiO₂, Ag, ZnO, graphene, carbon nanotubes (CNTs) and some others, in paints and coatings. It delves into the critical factors influencing dispersion, such as nanoparticle size, shape, concentration, and their distribution within the coating matrix.The review encompasses all stages of dispersion methods, including wetting, separation techniques, and stabilization. Regarding stabilization, both chemical and physical stabilization methods are discussed, along with their mechanisms, involving surface modification or functionalization of NMs, particularly tailored for aqueous and solvent‐based coatings and common resins (Acrylic, Urethane, Epoxy, Alkyd, etc.). Furthermore, common blending methods to fabricate uniform paints, coatings, and nanocomposites (NCPs) are examined. By providing a comprehensive understanding of the mechanisms governing NM dispersion and stabilization, this review facilitates the selection of appropriate surface modifications based on the specific resins or solvents, thereby enabling the fabrication of high‐performance paints and coatings. In summary, this review elucidates the essence of addressing the challenges associated with NM dispersion and stabilization, outlines methodologies employed, discusses findings regarding their effects on coating properties, and recommends tailored approaches for fabricating high‐performance paints and coatings.

Nanotechnology in the Fabrication of Advanced Paints and Coatings: Dispersion and Stabilization Mechanisms for Enhanced Performance

Nanotechnology in the Fabrication of Advanced Paints and Coatings: Dispersion and Stabilization Mechanisms for Enhanced Performance

New dispersion mechanism for oxide dispersion-strengthened steels by liquid metallurgy

The use of oxide dispersion-strengthened (ODS) alloys in demanding applications can effectively reduce parts’ weights, extend life of use, and enhance overall energy efficiency. But, the current manufacturing of ODS alloys has remained impractical for decades due to poor scalability and extremely high costs. Mass production of ODS steels by liquid metallurgy is therefore crucial to decrease their costs by several orders of magnitude and expand their potential applications. However, oxide nanoparticle (NP) dispersion in molten alloys presents fundamental challenges for liquid metallurgy due to the vastly dissimilar atomic properties between ionocovalent oxides and metals. Here we show, for the first time, that Y2O3 NPs are able to be dispersed in liquid 316L with a 1 % Nb addition. It was discovered that Nb-enriched interfacial layers exist around the Y2O3 NPs in solidified steels after slow cooling. Theoretical analyses reveal that the Nb-enriched interfacial layer induces a higher energy barrier and a significantly lower van der Waals attraction between oxide NPs and liquid Fe for the successful dispersion of oxide NPs in liquid steels. Moreover, Y2O3 and Al2O3 NPs were successfully dispersed in lean steels, such as Fe-Nb and low-C steels. This new dispersion mechanism of oxide NPs opens an exciting pathway for the economical mass manufacturing of various ODS alloys by liquid metallurgy for numerous applications.

Tracing Geographic and Molecular Footprints of Copepod Crustaceans Causing Multifocal Purple Spots Syndrome in the Caribbean Sea Fan Gorgonia ventalina

The recent rise in ocean temperatures, accompanied by other environmental changes, has notably increased the occurrence and spread of diseases in Octocorallia, many species of which are integral to shallow tropical and subtropical coral reef ecosystems. This study focuses on the understanding of these diseases, which has been largely limited to symptomatic descriptions, with clear etiological factors identified in only a fraction of cases. A key example is the multifocal purple spots syndrome (MFPS) affecting the common Caribbean octocoral sea fan Gorgonia ventalina, linked to the gall-forming copepods of the genus Sphaerippe, a member of the widespread family, Lamippidae. The specialized nature of these copepods as endoparasites in octocorals suggests the potential for the discovery of similar diseases across this host spectrum. Our investigation employed four molecular markers to study disease hotspots in Saint Eustatius, Curaçao, northwest and southwest Cuba, and Bonaire. This led to the discovery of a group of copepod species in these varied Caribbean locations. Importantly, these species are morphologically indistinguishable through traditional methods, challenging established taxonomic approaches. The observed diversity of symbionts, despite the host species’ genetic uniformity, is likely due to variations in larval dispersal mechanisms. Our phylogenetic analyses confirmed that the Lamippidae copepods belong to the order, Poecilostomatoida (Copepoda), and revealed their sister group relationship with the Anchimolgidae, Rhynchomolgidae, and Xarifiidae clades, known for their symbiotic relationships with scleractinian corals. These results add to our understanding of the evolutionary and ecological interactions of copepods and their hosts, and the diseases that they cause, and are important data in a changing climate.

Earwigs and woodlice as some of the world's smallest internal seed dispersal agents: Insights from the ecology of Monotropastrum humile (Ericaceae)

Societal Impact StatementThis study illuminates the underappreciated role of invertebrates in seed dispersal, extending beyond the well‐documented contributions of ants. Focusing on Monotropastrum humile (銀竜草 [silver dragon plant] or 水晶蘭 [crystal orchid]), a non‐photosynthetic plant known for its minuscule, dust‐like seeds, the present research uncovers their seed dispersal roles of woodlice and earwigs in Japan. Remarkably, these invertebrates include the smallest known endozoochorous seed dispersers.Summary Endozoochory, or internal seed dispersal through the digestive tracts of animals, has been less studied in invertebrates compared with vertebrates. Nonetheless, endozoochory is plausible whenever seeds are small enough for ingestion by frugivorous animals, suggesting a potential role for invertebrates in seed dispersal, especially for plants with minute seeds. Monotropastrum humile (Ericaceae), characterized by its fleshy fruits and dust‐like seeds, is known to utilize invertebrate agents such as camel crickets and cockroaches for seed dispersal. Here, we investigate this seed dispersal mechanism using time‐lapse photography, feeding experiments, and seed coat anatomy analysis, particularly focusing on interactions among undocumented invertebrate internal seed dispersers. Field observations indicated that in the studied population, M. humile fruits were primarily consumed by camel crickets, woodlice, and earwigs. Their effectiveness as seed dispersers varied, with camel crickets primarily acting as dispersers, whereas earwigs and woodlice were more inclined toward seed predation. Nonetheless, some seeds defecated by earwigs and woodlice remained intact, suggesting that they could also function as dispersal agents. The woodlouse Porcellio scaber is now recognized as the world's smallest internal seed dispersal agent. Combined with earlier discoveries, such as seed dispersal by camel crickets, cockroaches, and ants, and the fact that P. scaber is an exotic species in the study site, M. humile likely depends on a broad spectrum of local invertebrates. The engagement of multiple invertebrate dispersers may enhance seed dispersal across diverse habitats.

Performance and mechanism of organic solid-phase sediment composite plugging agent

The surface pipeline sediments of the Yingmai and Hade oil fields mainly contain substances such as asphalt and paraffin. The formation of sediment can increase the backpressure during pipeline transportation, and in severe cases, it can also lead to pipeline blockage. In order to solve this on-site situation, indoor experiments were conducted in the early stage, and an efficient organic unblocking system LXW was optimized and formulated. Based on this system, this article selects the wire mesh filtration method to evaluate the unblocking performance of LXW and on-site unblocking agents in the study and comparison of three evaluation methods. At the same time, based on the analysis of the chemical composition, microstructure, and melting point of organic sediments, from the perspectives of safety, environmental protection, and economic factors, further compares the performance and universality of the three unblocking systems, optimizes the process parameters of the LXW unblocking system, explores its stability and impact on the demulsification and dehydration of crude oil emulsions, and evaluates its safety performance. The LXW unblocking system has a more efficient unblocking effect and better universality, which can solve the problem of multiple block blockages on site. In addition, compared with existing unblocking agents, it has better economic benefits and is in line with the characteristics of low cost on site. On this basis, the dissolution and dispersion mechanism of the blockage system on sediment was studied through laser scattering system and fluorescence microscope, and its microscopic mechanism was further verified. At the same time, the oil-water interfacial tension under the action of the unblocking system was studied, and it was found that adding the agent can significantly reduce the equilibrium interfacial tension, which is of great significance for increasing production and injection.

Dynamic seismic signatures in a fluid‐saturated porous periodically layered medium considering effects of intrinsic anisotropy

AbstractThe interlayer wave‐induced fluid flow is an important mechanism for seismic attenuation and dispersion, as well as frequency‐dependent anisotropy, in the fluid‐saturated porous layered medium. This mechanism is closely related to the medium physical properties, and thus quantifying this mechanism is of significance for the seismic inversion of medium physical properties. Although numerous models have been proposed to quantify this mechanism, most models do not consider the effects of layer intrinsic anisotropy. To solve this problem, the effective complex‐valued and frequency‐dependent stiffness coefficients are derived for the fluid‐saturated porous medium composed of periodic transversely isotropic layers. Using the derived solutions, we study the effects of layer intrinsic anisotropy on seismic dispersion and attenuation, as well as frequency‐dependent anisotropy. It has been found that different matrix or fluid property contrasts between adjacent layers lead to different effects of intrinsic anisotropy. In addition, the effects of intrinsic anisotropy are also influenced by the fluid distribution when both matrix and fluid properties contrast among adjacent layers exist. In the low‐ and high‐frequency limits of wave‐induced fluid flow, our model reduces to the previous known results, which validates the correctness of our model. Our model can be applied in the seismic inversion of physical properties of reservoirs with intrinsic anisotropy, such as shale and tight sandstone reservoirs. In addition, our model can also be extended to cases with more complex intrinsic anisotropy and, thus, can be applied to complex anisotropic fractured reservoirs in the future.

Fine excipient materials in carrier-based dry powder inhalation formulations: The interplay of particle size and concentration effects

The contributions of fine excipient materials to drug dispersibility from carrier-based dry powder inhalation (DPI) formulations are well recognized, although they are not completely understood. To improve the understanding of these contributions, we investigated the influences of the particle size of the fine excipient materials on characteristics of carrier-based DPI formulations. We studied two particle size grades of silica microspheres, with volume median diameters of 3.31 μm and 8.14 μm, as fine excipient materials. Inhalation formulations, each composed of a lactose carrier material, one of the fine excipient materials (2.5% or 15.0% w/w), and a drug (fluticasone propionate) material (1.5% w/w) were prepared. The physical microstructure, the rheological properties, the aerosolization pattern, and the aerodynamic performance of the formulations were studied. At low concentration, the large silica microspheres had a more beneficial influence on the drug dispersibility than the small silica microspheres. At high concentration, only the small silica microspheres had a beneficial influence on the drug dispersibility. The results reveal influences of fine excipient materials on mixing mechanics. At low concentration, the fine particles improved deaggregation and distribution of the drug particles over the surfaces of the carrier particles. The large silica microspheres were associated with a greater mixing energy and a greater improvement in the drug dispersibility than the small silica microspheres. At high concentration, the large silica microspheres kneaded the drug particles onto the surfaces of the carrier particles and thus impaired the drug dispersibility. As a critical attribute of fine excipient materials in carrier-based dry powder inhalation formulations, the particle size demands robust specification setting.